GaN based microLED technology is particularly interesting for micro-displays for augmented reality. Beyond that, however, many additional applications exploiting the massively parallel nature of optical channels from microLED arrays are of interest. This includes microLED arrays for chip-based lensless microscopy, optogenetics, low power gas sensing, optical neuromorphic computing, high-speed maskless lithography or massively parallel line-of-sight communication in HPC centers (LIFI), replacing optical fibers. In order to drive large numbers of pixels at high frequencies in customized microLED arrays, the integration with a CMOS backplane chip is required.
The talk will mostly focus on chip processing and hybrid integration techniques for microLEDs and the opportunities for GaN based photonic integration in general, and GaN/CMOS integration in particular. First applications of specially designed microLED arrays in the field of optical neuromorphic computing will also be discussed. Test results include pattern recognition of hand-written digits from the MNIST dataset.
MicroLED arrays are arrangements of small, individually addressable LED pixels, which offer the possibility to obtain any desired illumination pattern with a high spatial and temporal control. In this work, we report on the advanced fabrication of micro- and nanoLED arrays and their system integration including electronics and graphical user interface. The combination of the chip-based LED array, electronics and software is called a MicroLED platform.
The light density output, homogeneity and switching behavior of the arrays are investigated. The system allows the modulation of the single light sources with a spatial resolution in the micron range and enables the programming of different light patterns at modulation frequencies up to the MHz range. The fully integrated system with microLED array and electronics is shown during presentation are now available as Structured Micro Illumination Platforms (SMILE) for applications from sensing to microscopy to quantum computing.
In this work, we study the optical emission from arrays of InGaN/GaN MQW nanofin and nanorod arrays with sizes ranging from a few micrometers down to sub-wavelength dimensions (i.e., nanometers). Such systems are of interest for developing arrays of single addressable nanoLEDs, which could be used to obtain a visible wavelength super-resolution microscope where the resolution is due to highly localized light spots with sub-wavelength LED-to-LED pitch.
We have used commercial full-wave Maxwell solvers (COMSOL, CST) to calculate the optical field emitted from a single nanoLED in a periodic array for a wavelength of 450 nm. Simulations on 11×11 nanoLED arrays with pitches of 200 nm up to 800 nm and diameters of down to 50 nm have been conducted, in which the dependency of the emission pattern on different structural parameters is studied. In case of small nanoLED array with very narrow pitch, a large optical cross-talk between the activated LED and its neighboring pixels was found. Moreover, in presence of cross-talks, test objects smaller than the LED pitch placed on its surface with influence of near field could potentially be resolved by evaluating the varied emission patterns obtained by different pixel activations. Routes to achieve higher localized optical fields and reduce optical cross-talk have been also investigated by modifying the nanoLED array structures (e.g., by introducing filling material among the LED pixels).
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